1. Technical Field
Aspects of this document relate generally to submersible light sources.
2. Background Art
Many examples of underwater work environments exist, requiring adequate lighting for workers to efficiently and successfully perform their designated functions. One example of an underwater work environment exists within the context of nuclear power plants. Nuclear power plants conventionally include nuclear reactor cavities and spent fuel pools. Such nuclear reactor cavities and spent fuel pools, in operation, typically contain water or other liquid solutions. It is often required of workers performing maintenance, repair and other work in nuclear reactor cavities and spent fuel pools to work under water. Due to the inherently hazardous nature of underwater work in nuclear reactor cavities and spent fuel pools, along with the sensitive nature of the materials to be handled, extensive illumination is typically required for the safety of workers and others. Workers in other underwater environments, such as in oceanographic or other underwater work, also typically have considerable underwater lighting requirements.
In the case of nuclear power plant workers, underwater work may occur during the regular operation of the plant, or during outages when nuclear fuel is changed. In either case, there must be sufficient light in a nuclear reactor cavity and/or spent fuel pool order to allow workers to safely perform their functions which may include, by way of non limiting example, identifying serial numbers on fuel bundles using underwater cameras. Of course, the specific nature of the underwater functions to be performed by workers may vary, whether in a nuclear power plant, or in another underwater work environment.
Conventionally, lighting sources for underwater work environments may include the use of incandescent lamps or HPS lamps. Both incandescent lamps and HPS lamps conventionally operate using either 120 or 240 Volts of Alternating Current (AC). While this arrangement may allow both incandescent bulbs and HPS bulbs to be used in conventional electrical configurations, the use of AC may also increase the risk of bodily injury or death to workers, as compared to other electrical current configurations such as Direct Current (DC).
The conventional use of incandescent lamps in underwater work environments may present several shortcomings. In particular, incandescent lamps may need to be replaced after about every 200 hours of operation. Also, in the case nuclear reactor cavities and spent fuel pools, lamp replacement may typically require the labor of two workers due to safety requirements. During a lamp change in a nuclear reactor cavity or spent fuel pool, workers may be undesirably exposed to radiation. Additionally, due to labor, material and other expenses, the cost of replacing a conventional underwater incandescent bulb in nuclear reactor cavities and spent fuel pools may approach or exceed several hundred dollars. While incandescent bulbs are typically inexpensive to purchase initially, they nevertheless convert electricity into light energy inefficiently compared to other light sources such as, by way of non-limiting example, High Pressure Sodium (HPS) and may thus be comparatively expensive to operate.
Lighting sources for underwater work environments may also include the use of High Pressure Sodium (HPS) lamps. HPS lamps have conventionally been used in underwater work environments due to their efficient light output per watt (lumens per watt) as compared to other light sources such as, by way of non-limiting example, incandescent lamps. Nevertheless, various shortcomings may also exist with regard to the conventional use of HPS lamps in underwater work environments. In particular, HPS lamps may need to be replaced after every 18 months. Like conventional incandescent bulbs, replacement of HPS bulbs may also typically require the labor of two workers, due to safety requirements. During a lamp change, whether incandescent or HPS, workers may be exposed to radiation. Additionally, due to labor, material and other expenses, the cost of replacing a conventional underwater HPS bulb in nuclear reactor cavities and spent fuel pools may approach or exceed a thousand dollars. Further shortcomings may also exist with regard to the use of HPS bulbs. Specifically, HPS bulbs conventionally contain mercury. A mercury spill can be merely inconvenient in the case of oceanographic or other non-nuclear underwater work, or may be catastrophic when occurring in a nuclear reactor cavity or spent fuel pool. Typically, a nuclear power plant desiring to use HPS bulbs in nuclear reactor cavities and spent fuel pools may be required to develop burdensome plans that would provide for the recovery of mercury in the event of HPS lamp breakage. Moreover, while HPS bulbs convert electricity into light energy more efficiently than incandescent bulbs, they may still be expensive to operate.
When incandescent lamps and/or HPS lamps are used in nuclear reactor cavities and spent fuel pools, they may be exposed to gamma radiation and high temperatures. Typically, when incandescent and/or HPS bulbs used in nuclear reactor cavities and spent fuel pools require replacement, the discarded bulbs may be required to be disposed of as “radioactive waste,” at significant expense, due to their prior contact with gamma radiation.